Trace metal free CTD water column profiles (temperature, salinity, dissolved oxygen, optical backscatter, beam transmittance and attenuation, PAR, pH, and chlorophyll-a fluorescence) collected in the Norwegian and Barents Sea in July-August 2023 on cruise DY167 (GEOTRACES GApr19).

This dataset contains in-situ temperature, salinity, dissolved oxygen, optical backscatter, beam transmittance and attenuation, PAR, pH, and chlorophyll-a fluorescence data from 22 downcast trace-metal free CTD profiles. The measurements were collected during cruise DY167 (GEOTRACES cruise GApr19) in July-August 2023 in the Norwegian and Barents Seas and cover the relatively warm Atlantic Water inflow, fresher water on the Spitzbergen Bank, coastal/glacial outflow around Svalbard, and Arctic water around sea ice. The trace metal free setup comprised a Sea-Bird Electronics (SBE) 9 plus underwater unit, and an SBE 11 plus deck unit; all of which were mounted on a titanium 24-way carousel. Attached to the underwater unit were two SBE 3P temperature sensors, two SBE 4C conductivity sensors, one Paroscientific Digiquartz pressure sensor, one SBE 43 dissolved oxygen sensor, two CTG PAR sensors, one WETLabs BBRTD light scattering sensor, one Valeport altimeter, one CTG Aquatracka MKIII fluorometer, one WETLabs C-star transmissometer and one AMT Deep pH sensor. Raw data were initially extracted and processed using Seabird Data Processing Software. Modules DatCnv, WildEdit, Filter, AlignCTD, CellTM and Derive were all run. Custom Matlab routines were then used to remove out of water and surface soak values, to filter anomalous data points and to average the profiles onto a 1 decibar pressure grid. Salinity and chlorophyll-a were both calibrated against independent in-situ samples. These data were collected to better determine how temperature, light, nutrients, and iron control the distribution and activity of nitrogen fixing organisms in the Arctic Ocean. This dataset was generated by the National Oceanography Centre (NOC) under Natural Environment Research Council (NERC) Discovery grant Nitrogen fixation in the Arctic Ocean, N-ARC (grant numbers NE/T000570/1 and NE/T001240/1).